The present invention relates to methods and apparatus for facilitating data communication among computer subsystems. More particularly, the present invention relates to improved insulation displacement connectors that advantageously permit interspersed ground conductor ribbon cables to be employed for data communication among computer subsystems.
The use of ribbon cables and their connectors to facilitate data communication between computer subsystems is well known. To facilitate discussion, FIG. 1 illustrates a ribbon cable assembly 100, including five parallel insulated conductors 112, 114, 116, 118, and 120. Insulated conductors 112-120 are typically employed to carry data, control signals, and the like between subsystem 102 and subsystem 104. Although only five conductors are shown to simplify the illustration, ribbon cable assembly 100 may in practice include any number of parallel conductors required for data transmission.
The conductors of ribbon cable assembly 100 are coupled to female insulation displacement-type connectors (IDC) 122 and 124 at their ends. As shown, female IDC 122 includes five apertures 132, 134, 136, 138, and 140 at its mating face 141. The apertures are configured to mate with respective contacts (e.g., pins) 142, 144, 146, 148, and 150 of a complementary connector 152 disposed on subsystem 102. Since IDC 122 is a female connector, complementary connector 152:, which is complementary in gender, is a male connector. The female IDC is discussed in greater detail in FIGS. 2A-E herein. A similar arrangement exists between female IDC 124 and male connector 162 (disposed on subsystem 104 in FIG. 1). When female IDCs 122 and 124 are coupled to their respective male connectors, each contact (e.g., pin) on male connector 152 of subsystem 102 is in electrical communication, via ribbon cable assembly 100, with its counterpart contact on male connector 162 of subsystem 104 to permit data transfer to take place therebetween.
To facilitate further discussion of the female IDC connector that couples to the conductors of the ribbon cable assembly, FIGS. 2A-E illustrate in detail an exemplary 40-contact female IDC connector 200. Female IDC connector 200 may represent, for example, a female connector for use with the 40-conductor ribbon cable assemblies that are currently popular in coupling hard disks to their hard disk controllers in accordance with the well defined 40-contact ATA (Advanced Technology or "AT" Attachment) specification. Female IDC 200 may represent, for example, a 3417-7000 connector, available from 3M Corp. of St. Paul, Minn.
In FIG. 2A, a schematic- view of the ribbon-contacting side of female IDC 200, i.e., the side at which the conductors terminate, is illustrated. Female IDC 200 includes 40 apertures (labeled A1-A40 in FIG. 2A). A mating side view of female IDC 200, i.e., the side to which a male connector is coupled, is illustrated in FIG. 2B. In FIG. 2B, apertures A1-A40 of FIG. 2A are depicted as seen from the mating side. By conforming the location, dimension, and signal assignment of each aperture to a well-established specification, female IDC 200 may be interchangeably coupled to any male conductor conforming to the same specification.
Within each of apertures A1-A40, there is disposed a conductor coupling structure 202 (shown in greater detail in FIG. 2C), which includes an insulation displacement structure 250 and a contact engaging structure 252. When the ribbon-contacting side of female IDC 200 is placed against a ribbon cable, an insulated conductor of the ribbon cable is disposed between leaves 254(a) and 254(b) of insulation displacement structure 250. By pressing the ribbon cable to the ribbon-contacting side of female IDC 200, the multiple leaves 254(a) and 254(b) of conductor coupling structures 202 of the female IDC cut through the insulation surrounding the parallel conductors C1-C40 of the ribbon cable, allowing individual conductor coupling structures 202 to be in direct electrical contact with individual exposed conductors.
Contact engaging structure 252, which may be offset from the plane formed by conductor coupling structure 202, is designed to engage a male connector pin when the pin is inserted into the aperture from the mating side of the female IDC, thereby allowing the pin to be in electrical contact with a conductor of the ribbon cable (which is in direct electrical contact with conductor coupling structure 202 as described earlier). FIG. 2D shows, in one example, the manner in which contact engaging structure 252 of conductor coupling structure 202 engages a pin 256 of the male connector to make an electrical connection therewith.
To further facilitate ease of illustration and comprehension, FIG. 2E is an enlarged schematic view of aperture A1 of FIG. 2A as seen from the ribbon-contacting side, illustrating the general relationship between the aperture, the conductor coupling structure, the conductor, and the pin (which is associated with the male connector and is inserted into the aperture from the mating side). In FIG. 2E, a conductor 182 of the ribbon cable is shown disposed in between leaves 254(a) and 254(b) of insulation displacement structure 250 of conductor coupling structure 202 (discussed in connection with FIG. 2C earlier). Contact engaging structure 252 of FIG. 2C is also shown within pin receptacle area 260 of the aperture. When a pin (illustrated by the dashed outline) of the male conductor is inserted into pin receptacle area 260, the electrical contact is made between the pin and contact engaging structure 252 at point 262 as shown. As can be appreciated from the foregoing, the coupling of the numerous insulated conductors of a ribbon cable to its female connector can be performed in a single crimping step when insulation displacement-type connectors are employed, thereby saving labor and cost. For this reason, insulation displacement-type connectors are widely used to create ribbon cable assemblies.
For relatively slow ATA data transfer rates, standard ribbon cables (i.e., those having signal-bearing conductors disposed immediately adjacent to one another) work adequately. When the data transfer rates increase, e.g., to facilitate communication between high performance subsystems or during data bursts between even relatively slow subsystems, the inductive cross-talk between adjacent signal-bearing conductors of the ribbon cable degrades the signals thereon. If the inductive cross-talk is excessive, some of the data being transmitted via the ribbon cable assembly may be corrupted. Accordingly, inductive cross-talk limits the data transfer rates between subsystems that are interconnected by a standard ribbon cable.
It is generally known that the use of interspersed ground conductors in a ribbon cable reduces the inductive crosstalk between adjacent signal-bearing conductors. FIG. 3 illustrates an interspersed ground ribbon cable assembly 302, in which the five signal-bearing conductors 304 are shielded from one another by a plurality of ground conductors 306. By shielding the signal-bearing conductors from one another, inductive cross-talk is reduced, thereby permitting data communication to take place it a relatively high rate over interspersed ground ribbon cable assembly 302 and/or increasing the signal-to-noise ratio of the data transmitted over interspersed ground ribbon cable assembly 302.
It is a relatively simple matter to increase the number of conductors in a given ribbon cable such that every other conductor is non signal-bearing and grounded, thereby creating an interspersed ground ribbon cable. However, the coupling of conductors of the resultant interspersed ground ribbon cable with its female IDCs (e.g., female IDCs 122 and 124) has, up to now, presented manufacturers with many difficulties. This is because, as mentioned earlier, the number, location, dimension, and signal assignment of each aperture in the female IDC typically conform to already-established specification and preferably remain unchanged for compatibility reasons even as shielding ground conductors are added. In other words, the interspersed ground conductors of the interspersed ground ribbon cable, e.g., ground conductors 306 in FIG. 3, are preferably coupled to ground without requiring changes to the female IDC, at least as far as the mating side of the female IDC is concerned.
In the prior art, the fabrication of an interspersed ground ribbon cable assembly typically involves a significant amount of manual labor. In one case, after the female IDCs are pressed onto their signal bearing conductors, the remaining interspersed ground conductors are stripped off their insulation and then manually soldered together. The interconnected ground conductors are then coupled to ground, e.g., via the grounded chassis of the computer system. As can be appreciated from the foregoing, the labor intensive nature of the prior art technique defeats the very purpose of using insulation displacement connectors, i.e., to simplify fabrication and reduce manufacturing cost. Because of the additional manual labor required, interspersed ground ribbon cable assemblies manufactured in accordance with the prior art techniques tend to be costly.
In view of the foregoing, there are desired improved insulation displacement-type connector designs that simplify the coupling with interspersed ground conductor ribbon cables. Further, the improved insulation-displacement type connectors preferably require no changes to the existing complementary connector to which it is coupled in order to facilitate backward compatibility with existing subsystems.